Various techniques have been proposed for predicting seismic events such as earthquakes in particular. Generally speaking, the methods proposed are based on the measurement of variations in the magnetic field, earth currents, propagation speed and frequency.
U.S. Pat. No. 4,612,506 in the name of Varotsos and others illustrates, for example, an earthquake prediction method based on transitory variations in electrical earth currents, detected by electrodes buried in the ground. The method involves selecting parts of the abovementioned transitory variations in electrical earth currents for preset frequency ranges. The amplitude of these currents is then compared with preset standard values, in order to obtain a forecast on intensity, dislocation and/or time of occurrence of an imminent earthquake.
Another seismic event prediction system, illustrated in patent EP 623.221 in the name of Röder and others, uses a measurement device that records fluctuations in the electric field, detected by one or more electrical conductivity probes, with amplification by means of an electronic circuit and subsequent treatment in a processing unit. Potential fluctuations are produced in an empty space near to the surface of the ground and are recorded in relation to a reference potential existing on the surface.
Patent EP 457.788 in the name of Love and others illustrates a method for real estate surveillance such as public and industrial buildings, which involvess measuring variations in the electrostatic field, within the material to be monitored, by means of a suitable probe, and amplifying the HF components of the measurement signal.
Another method, illustrated in U.S. Pat. No. 4,837,582, includes detecting the magnetic waves that are generated before an earthquake occurs by means of an aerial located on the land or on the seabed.
However, known methods are only able to predict the occurrence of an earthquake, its epicentre and intensity or magnitude in an extremely vague way.